In photography and imaging systems, lens selection not only affects image quality, but also directly impacts the reliability and lifespan of the entire system. This article will analyze how to choose the most suitable lens for cameras and camera modules from the perspective of reliability engineering.

1, Understand the correlation between basic lens parameters and reliability
The choice of focal length directly affects the applicability and structural reliability of the device. Short focal length lenses (wide-angle lenses) typically have simpler optical structures and fewer mechanical components, resulting in fewer potential failure points. The complex optical design of telephoto lenses means more moving parts, making them more prone to problems such as wear and tear of the focusing mechanism in vibration environments.

The aperture size not only determines the amount of light entering, but also relates to the durability of the system. Although the large aperture lens (f/1.4-f/2.8) provides better low light performance, its precise optical components are more sensitive to dust and moisture. In industrial applications, medium aperture (f/4-f/8) lenses often exhibit better environmental tolerance.

Resolution and MTF curve are key indicators for evaluating the optical performance of a lens. High resolution requirements typically require more complex optical designs, which increase the number of lenses and reduce overall reliability. According to the "series system reliability theory", adding one lens is equivalent to adding a potential fault point in the system.

2, Application scenarios determine reliability requirements
The reliability requirements for lenses vary significantly in different application environments:

Industrial testing systems require special attention to:

Anti vibration design: Choose a lens with a sturdy metal barrel

Dust proof seal: IP rating of at least IP52

Temperature stability: The working range usually requires -10 ° C to 50 ° C

Key considerations for outdoor surveillance cameras:

24/7 protection: IP66 or higher protection level

Anti fog design: built-in heating element or special coating

UV resistance: special coating to prevent sunlight degradation

Special requirements for medical endoscopes:

Biocompatible material

High pressure sterilization tolerance

Structural integrity of miniaturized design

3, Mechanical interface and installation reliability
The selection of C interface and CS interface is not only related to compatibility, but also affects mechanical stability. Incorrect interface matching can lead to flange distance mismatch, which not only affects imaging, but also causes thread wear and optical axis offset during long-term use.

The active alignment and passive alignment processes directly affect the reliability of the module. Active Alignment (AA) technology, although expensive, can achieve precise alignment of ± 0.01 °, significantly improving product consistency and long-term stability.

Torque control during installation is crucial. Excessive tightening can cause deformation of the lens barrel, affecting imaging quality; Insufficient torque may cause looseness in vibration environments. The recommended installation torque for a typical C-interface lens is 1.2-1.5N · m.

4, Environmental adaptability design
Temperature changes can cause the lens material to expand/contract, affecting focusing stability. High quality industrial lenses use special alloy barrels and optical glass to ensure consistent performance over a wide temperature range. The temperature coefficient (Δ f/° C) is a key parameter for evaluating this performance.

The dustproof and moisture-proof design level needs to match the actual environment. IP6X indicates complete dust-proof, while the second digit represents waterproof rating (such as IPX4 splash proof). It is recommended to have at least IP54 rating for applications in tropical regions.

The resistance to impact and vibration is particularly important for mobile devices. The MIL-STD-810G standard provides relevant testing methods, and industrial grade lenses can typically withstand at least 10G of impact and 5-500Hz of random vibration.

5, Material selection and long-term reliability
The material of the lens barrel directly affects thermal stability and mechanical strength:

Aluminum alloy: lightweight and low-cost, but with a high coefficient of thermal expansion

Stainless steel: excellent strength and corrosion resistance, but heavy in weight

Engineering plastics: Good impact resistance, suitable for consumer grade products

The type of optical glass affects environmental tolerance:

Calcium fluoride (CaF2) crystal: excellent color correction, but prone to deliquescence

Environmentally friendly glass: free of lead and arsenic, compliant with RoHS standards

Fused silica: extremely low thermal expansion, suitable for high-precision applications

Coating technology determines the wear resistance and anti reflection performance of lenses:

Multi layer coating: reduces glare and improves light transmittance

Oil repellent coating: easy to clean, maintains long-term optical performance

Diamond coating: hardness up to 9H, extremely wear-resistant

6, Supplier evaluation and reliability verification
Supplier qualification review should include:

ISO 9001 Quality Management System Certification

Environmental testing capabilities (such as salt spray, temperature cycling, etc.)

Traceability Management System for Key Components

The reliability testing project should cover:

Mechanical durability test (such as 5000 autofocus cycles)

Environmental Stress Screening (ESS)

Accelerated Life Test (ALT)

Failure mode analysis capability is an important indicator for evaluating suppliers, including:

Fault Tree Analysis (FTA) capability

Root Cause Analysis (RCA) Report Quality

Effectiveness of Corrective and Preventive Actions (CAPA)

7, Balancing cost and reliability strategy
Total Cost of Ownership (TCO) analysis should consider:

Initial procurement cost

Expected maintenance frequency and cost

System shutdown loss

Standardization strategy can improve reliability and reduce costs:

Reduce the number of lens models

Adopting industry standard interfaces

Establish universal testing standards

The preventive maintenance plan should be based on:

Manufacturer's recommended maintenance cycle

Severity of actual usage environment

Historical fault statistics data